Flat panel direct methanol fuel cell and method for making the same

ABSTRACT

A flat panel DMFC (direct methanol fuel cell) includes an integrated cathode electrode sheet, a set of membrane electrode assemblies, an intermediate bonding layer, an integrated anode electrode sheet, and a fuel container base. The integrated cathode/anode electrode sheets are manufactured by using PCB compatible processes.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates generally to the field of fuel cells. Moreparticularly, the present invention relates to a flat panel DirectMethanol Fuel Cell (DMFC) and method of making the same.

2. Description of the Prior Art

A fuel cell is an electrochemical cell in which a free energy changeresulting from a fuel oxidation reaction is converted into electricalenergy. Fuel cells utilizing methanol as fuel are typically calledDirect Methanol Fuel Cells (DMFCs), which generate electricity bycombining gaseous or aqueous methanol with air. DMFC technology hasbecome widely accepted as a viable fuel cell technology that offersitself to many application fields such as electronic apparatuses,vehicles, military equipment, the aerospace industry, and so on.

DMFCs, like ordinary batteries, provide DC electricity from twoelectrochemical reactions. These reactions occur at electrodes (orpoles) to which reactants are continuously fed. The negative electrode(anode) is maintained by supplying methanol, whereas the positiveelectrode (cathode) is maintained by the supply of air. When providingcurrent, methanol is electrochemically oxidized at the anodeelectrocatalyst to produce electrons, which travel through the externalcircuit to the cathode electrocatalyst where they are consumed togetherwith oxygen in a reduction reaction. The circuit is maintained withinthe cell by the conduction of protons in the electrolyte. One moleculeof methanol (CH3OH) and one molecule of water (H2O) together store sixatoms of hydrogen. When fed as a mixture into a DMFC, they react togenerate one molecule of CO2, 6 protons (H+), and 6 electrons togenerate a flow of electric current. The protons and electrons generatedby methanol and water react with oxygen to generate water. Themethanol-water mixture provides an easy means of storing andtransporting hydrogen, and is much better than storing liquid or gaseoushydrogen in storage tanks. Unlike hydrogen, methanol and water areliquids at room temperature and are easily stored in thin walled plasticcontainers. Therefore, DMFCs are lighter than their most closely relatedfuel cells, hydrogen-air fuel cells.

FIG. 1 and FIG. 2 illustrates a conventional DMFC 10, wherein FIG. 1 isa plan view of the conventional DMFC 10 and FIG. 2 is a cross-sectionalview of the conventional DMFC 10 along line 1-1 of FIG. 1. As shown inFIG. 1 and FIG. 2, the conventional DMFC 10 comprises a bipolar plateletassembly 12 and a fuel container 14. The bipolar platelet assembly 12comprises an upper frame 51, lower frame 52, cathode wire lath 121, aplurality of bended bipolar wire laths 122, 123, 124, 125, an anode wirelath 126, and membrane electrode assembly (MEA) 131, 132, 133, 134, 135interposed between corresponding wire laths. The upper frame 51, thelower frame 52, the cathode wire lath 121, the plural bended bipolarwire laths 122, 123, 124, 125, the anode wire lath 126, and the MEA 131,132, 133, 134, 135 are adhesively stacked together to produce the stackstructure as shown in FIG. 2. Typically, epoxy resin 53 or the like isused in between adjacent MEA, thereby forming five basic cell units 21,22, 23, 24 and 25. As known in the art, the cathode wire lath 121,bended bipolar wire laths 122, 123, 124, 125, and the anode wire lath126 are titanium meshes treated by gold plating, and are thereforecostly.

The basic cell unit 21 of the prior art DMFC 10 consists of the cathodewire lath 121, MEA 131, and the bended bipolar wire lath 122. The basiccell unit 22 consists of the bended bipolar wire lath 122, whichfunctions as a cathode of the cell unit 22, MEA 132, and the bendedbipolar wire lath 123, which functions as an anode of the cell unit 22.The basic cell unit 23 consists of the bended bipolar wire lath 123,which functions as a cathode of the cell unit 23, MEA 133, and thebended bipolar wire lath 124, which functions as an anode of the cellunit 23. The basic cell unit 24 consists of the bended bipolar wire lath124, which functions as a cathode of the cell unit 24, MEA 134, and thebended bipolar wire lath 125, which functions as an anode of the cellunit 24. The basic cell unit 25 consists of the bended bipolar wire lath125, which functions as a cathode of the cell unit 25, MEA 135, and thebended bipolar wire lath 126, which functions as an anode of the cellunit 25. Typically, each of the basic cell units 21, 22, 23, 24 and 25provides a voltage of 0.6V, such that DMFC 10 comprising five seriallyconnected basic cell units 21, 22, 23, 24 and 25 can provide a totalvoltage of 3.0V (0.6V×5=3.0V).

However, the above-described conventional DMFC 10 has several drawbacks.First, the bipolar platelet assembly 12 is too thick and thus unwieldyto carry. Furthermore, as mentioned, the cost of producing theconventional DMFC 10 is high since the cathode wire lath 121, bendedbipolar wire laths 122, 123, 124, 125, and the anode wire lath 126 aretitanium meshes treated by gold plating. Besides, the throughput of theconventional DMFC 10 is low because the bipolar wire laths 122, 123,124, 125 are bended manually before mounting on the upper and lowerframes. In light of the above, there is a need to provide a thin,inexpensive, and highly integrated DMFC that is capable of achieving thescale of mass production.

SUMMARY OF INVENTION

It is therefore the primary objective of the present invention toprovide an improved thin flat panel type DMFC to solve theabove-mentioned problems.

It is another objective of the present invention to provide a method forfabricating a thin and highly integrated DMFC, thereby achieving thescale of mass production and thus saving cost, wherein the method forfabricating the highly integrated DMFC is compatible with standard PCB(printed circuit board) processes.

It is another objective of the present invention to provide a method forassembling a flat panel DMFC.

According to the claimed invention, a flat-panel direct methanol fuelcell (DMFC) is provided. The present invention DMFC comprises anintegrated cathode electrode sheet, a membrane electrode assembly (MEA)unit, an intermediate bonding layer, an integrated anode electrodesheet, and a fuel container. The integrated cathode electrode sheetcomprises a first substrate, a plurality of cathode electrode areas, aplurality of first conductive via through holes, wherein the cathodeelectrode areas is electroplated on a front side and backside of thefirst substrate and has a plurality of apertures therein, wherein thefirst conductive via through holes are disposed outside the cathodeelectrode areas and is electrically connected to respective cathodeelectrode areas with a conductive wire. The membrane electrode assembly(MEA) unit comprises a plurality of proton exchange membranescorresponding to the plurality of cathode electrode areas. Theintermediate bonding layer comprises at least one bonding sheet, whereinthe intermediate bonding layer comprises a plurality of openings forrespectively accommodating the plurality of proton exchange membranes,and a plurality of second conductive via through holes that are alignedwith the first conductive via through holes. The integrated anodeelectrode sheet comprises a second substrate, a plurality of anodeelectrode areas corresponding to the plurality of cathode electrodeareas, and a plurality of third conductive via through holescorresponding to the second conductive via through holes.

According to one aspect of the present invention, a method forfabricating an integrated cathode electrode sheet of a flat-panel directmethanol fuel cell is provided. The method comprises the steps of:

-   -   (1) providing a CCL (copper clad laminate) substrate comprising        a base layer, a first copper layer laminated on an upper surface        of the base layer, and a second copper layer laminated on a        lower surface of the base layer;    -   (2) drilling the CCL substrate within pre-selected electrode        areas to form a plurality of apertures through the first copper        layer, the base layer and the second copper layer;    -   (3) chemically depositing a third copper layer on the CCL        substrate and interior sidewalls of inside the apertures;    -   (4) forming a patterned resist layer on the CCL substrate to        expose the pre-selected electrode areas;    -   (5) using the patterned resist layer as a plating mask,        performing an electroplating process to electroplate a fourth        copper layer within the expose the pre-selected electrode areas        and area not covered by the patterned resist layer, and then        electroplating a Sn/Pb layer on the fourth copper layer;    -   (6) stripping the patterned resist layer;    -   (7) performing a copper etching process to etch away the third        copper layer and the first and second copper layer that are not        covered by the Sn/Pb layer; and    -   (8) removing the Sn/Pb layer to expose the fourth copper layer.

In addition, the present invention discloses a method for assemblingflat panel direct methanol fuel cells, the method comprising: providingan integrated cathode electrode plate comprising a first substrate, aplurality of cathode electrode areas, and a first conductive via throughhole, wherein the cathode electrode areas are electroplated on both thefront and the backside of the first substrate and have a plurality ofapertures therein, wherein the first conductive via through hole isdisposed outside the cathode electrode areas and is electronicallyconnected to the respective cathode electrode areas with a conductivewire; providing a plurality of proton exchange membranes correspondingto the plurality of cathode electrode areas; providing an intermediatebonding layer comprising at least one bonding sheet, wherein theintermediate bonding layer comprises a plurality of openings forrespectively accommodating the plurality of proton exchange membranes,and a second conductive via through hole that is aligned with the firstconductive via through hole; providing an integrated anode electrodeplate comprising a second substrate, a plurality of anode electrodeareas corresponding to the plurality of cathode electrode areas, and athird conductive via through hole corresponding to the first conductivevia through hole; stacking the integrated cathode electrode plate, theplurality of proton exchange membranes, the intermediate bonding layer,and the integrate anode electrode plate in order; aligning andpenetrating the first conductive via through hole, the second conductivevia through hole, and the third conductive via through hole by using ametal plug; utilizing the metal plug to conduct and to fix the firstconductive via through hole, the second conductive via through hole, andthe third conductive via through hole in place for forming a bipolar/MEAassembly; and combining the bipolar/MEA assembly with a fuel container.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plain view of the conventional Direct Methanol Fuel Cell.

FIG. 2 is a cross-sectional view of the conventional Direct MethanolFuel Cell along line 1-1 of FIG. 1.

FIG. 3 is a perspective, exploded diagram illustrating a flat panelDirect Methanol Fuel Cell with five serially connected basic cell unitsin accordance with one preferred embodiment of the present invention.

FIG. 4 to FIG. 12 illustrate a method for fabricating integrated thincathode electrode sheet and integrated thin anode electrode sheet of theDMFC according to this invention.

FIG. 13 and FIG. 14 are side-view diagrams showing the means by whichthe integrated thin cathode electrode sheet, the MEA unit, theintermediate bonding layer, and the integrated thin anode electrodesheet are assembled according to another embodiment of the presentinvention.

FIG. 15 to FIG. 17 are side-view diagrams showing the means by which theintegrated thin cathode electrode sheet, the MEA unit, the intermediatebonding layer, and the integrated thin anode electrode sheet areassembled according to another embodiment of the present invention.

FIG. 18 is a perspective diagram showing a stage before the integratedthin cathode electrode sheet, the MEA unit, the intermediate bondinglayer, and the integrated thin anode electrode sheet are laminated.

FIG. 19 is a perspective diagram showing a stage after the integratedthin cathode electrode sheet, the MEA unit, the intermediate bondinglayer, and the integrated thin anode electrode sheet are laminated.

DETAILED DESCRIPTION

Please refer to FIG. 3. FIG. 3 is a perspective, exploded diagramillustrating a flat panel DMFC 20 with five serially connected basiccell units in accordance with one preferred embodiment of the presentinvention. It is to be understood that the flat panel DMFC 20 with fiveserially connected basic cell units is merely an exemplary embodiment.Depending on the requirements of the applied apparatuses, other numbersof basic cell units such as ten or twenty may be used. As shown in FIG.3, the present invention flat panel DMFC 20 generally comprises anintegrated thin cathode electrode sheet 200, Membrane Electrode Assembly(MEA) unit 300, intermediate bonding layer 400, integrated thin anodeelectrode sheet 500, and a fuel container 600.

The integrated thin cathode electrode sheet 200 comprises a substrate210, cathode electrode areas 201, 202, 203, 204, and 205, and conductivevia through holes 211, 212, 213, 214, and 215. Preferably, on thesurface area of the substrate 210 outside the cathode electrode areas201, 202, 203, 204, and 205, and the conductive via through hole 211,212, 213, 214, and 215, a layer of solder resist is coated thereon. Atthe corners of the substrate 210, mounting through holes 221, 222, 223,and 224 are provided. It is noteworthy that the integrated thin cathodeelectrode sheet 200 is fabricated by using PCB compatible processes. Thesubstrate 210 may be made of ANSI-grade glass fiber reinforced polymericmaterials such as FR-1, FR-2, FR-3, FR-4, FR-5, CEM-1 or CEM-3, but notlimited thereto. Each of the cathode electrode areas 201, 202, 203, 204,and 205, on which a plurality of through holes are formed, is defined bya patterned copper foil. The opening ratio of each of the cathodeelectrode areas 201, 202, 203, 204, and 205, which is the ratio of thesurface area of the through holes to the area of each of the cathodeelectrode areas, is preferably no less than 50%.

The conductive via through hole 212 is electrically connected to thecathode electrode area 201 with the conductive wire 250. The conductivevia through hole 213 is electrically connected to the cathode electrodearea 202 with the conductive wire 251. The conductive via through hole214 is electrically connected to the cathode electrode area 203 with theconductive wire 252. The conductive via through hole 215 is electricallyconnected to the cathode electrode area 204 with the conductive wire253. The cathode electrode area 205 is electrically connected to apositive (cathode) electrode node 261, which, in operation, is furtherelectrically connected with an external circuit by conductive wire 254.The conductive via through hole 211, which acts as a negative (anode)electrode node of the DMFC 20, is electrically connected with theexternal circuit and positive (cathode) electrode node 261 in operation.

The MEA unit 300 comprises a first proton exchange membrane 301, asecond proton exchange membrane 302, a third proton exchange membrane303, a fourth proton exchange membrane 304, and a fifth proton exchangemembrane 305, corresponding to the cathode electrode areas 201, 202,203, 204, and 205. Each of the proton exchange membranes 301, 302, 303,304, and 305 may use commercially available proton conducting polymerelectrolyte membranes, for example, Nafion™, but not limited thereto.

The intermediate bonding layer 400 comprises at least one bonding sheet,which may be made of Prepreg B-stage resin, which is an ordinarymaterial in PCB processes. The Prepreg B-stage resin may be completelycured at about 140° C. for process time period of about 30 minutes.Corresponding to the proton exchange membranes 301, 302, 303, 304, and305, five openings 401, 402, 403, 404, and 405 are provided on theintermediate bonding layer 400 for fitly accommodating respective protonexchange membranes. At a side of the opening 401 corresponding to theconductive via through hole 211 of the substrate 210, as specificallyindicated in FIG. 3, a conductive via through hole 411 is provided. At aside of respective openings 402, 403, 404, and 405 corresponding to theconductive via through holes 212, 213, 214, and 215, conductive viathrough holes 412, 413, 414, and 415 are provided. In another case, theintermediate bonding layer 400 may further a thin supporting layer thatis made of glass fiber reinforced polymeric materials such as FR-1,FR-2, FR-3, FR-4, FR-5, CEM-1 or CEM-3. At the corners, corresponding tothe mounting through holes 221, 222, 223, and 224 of the substrate 210,there are mounting through holes 421, 422, 423, and 424 provided.

The integrated thin anode electrode sheet 500 comprises a substrate 510,anode electrode areas 501, 502, 503, 504, and 505, and conductive pads511, 512, 513, 514, and 515. It is noteworthy that the anode electrodeareas 501, 502, 503, 504, 505 are defined simultaneously with theconductive pads 511, 512, 513, 514, 515. At the corners of the substrate510, corresponding to the mounting through holes 221, 222, 223, and 224of the substrate 210, there are mounting through holes 521, 522, 523,and 524 provided. The integrated thin anode electrode sheet 500 isfabricated by using PCB compatible processes. Likewise, the substrate510 may be made of ANSI-grade glass fiber reinforced polymeric materialssuch as FR-1, FR-2, FR-3, FR-4, FR-5, CEM-1, CEM-3 or the like. Each ofthe anode electrode areas 501, 502, 503, 504, and 505, on which aplurality of through holes are formed, is defined by a patterned copperfoil. The opening ratio of each of the anode electrode areas ispreferably no less than 50%.

The fuel container 600 has fuel channel 601 and mounting through holes621, 622, 623, and 624 corresponding to the mounting through holes 221,222, 223, and 224 of the substrate 210. The fuel container 600 may bemade of polymeric materials such as epoxy resin, polyimide, or Acrylic.The fuel channel 601 may be fabricated by using conventional mechanicalgrinding methods or plastic extrusion methods.

When assembling, the proton exchange membranes 301, 302, 303, 304, and305 are fitly installed within the openings 401, 402, 403, 404, and 405of the intermediate bonding layer 400. The intermediate bonding layer400, together with the installed proton exchange membranes 301, 302,303, 304, and 305, is then sandwiched by the integrated thin cathodeelectrode sheet 200 and the integrated thin anode electrode sheet 500.The resultant laminate stack consisting in the order of the integratedthin cathode electrode sheet 200, intermediate bonding layer 400 (andinstalled MEA unit 300), and the integrated thin anode electrode sheet500 is then mounted on the fuel container 600.

The conductive via through holes 211, 212, 213, 214 and 215 of theintegrated thin cathode electrode sheet 200 are aligned, and in contact,with the respective conductive via through holes 411, 412, 413, 414 and415 of the intermediate bonding layer 400, which are aligned with theconductive pads 511, 512, 513, 514 and 515 of the integrated thin anodeelectrode sheet 500. Conventional soldering process may be used toelectrically connected and fix the aligned conductive through holes suchas conductive via through holes 211, 411, and conductive pad 511, and soon. By doing this, the cathode electrode area 201 of the integrated thincathode electrode sheet 200 is electrically connected to the anodeelectrode area 502 of the integrated thin anode electrode sheet 500through the conductive path constituted by the conductive wire 250, thesoldered conductive via through holes 212 and 412, and the conductivepad 512 of the integrated thin anode electrode sheet 500. The cathodeelectrode area 202 of the integrated thin cathode electrode sheet 200 iselectrically connected to the anode electrode area 503 of the integratedthin anode electrode sheet 500 through the conductive path constitutedby the conductive wire 251, the soldered conductive via through holes213 and 413, and the conductive pad 513 of the integrated thin anodeelectrode sheet 500, and so on. The conductive via through hole 211 ofthe integrated thin cathode electrode sheet 200, which acts as thenegative electrode of the DMFC 20, is electrically connected to theanode electrode area 501 of the integrated thin anode electrode sheet500 through the conductive via through hole 411 of the intermediatebonding layer 400.

It is advantageous to use the present invention because the DMFC 20 hasintegrated thin cathode electrode sheet 200 and integrated thin anodeelectrode sheet 500, which reduce the thickness as well as theproduction cost of the DMFC 20. No bended bipolar wire lath is needed.The integrated thin cathode electrode sheet 200 and integrated thinanode electrode sheet 500 are fabricated by using PCB compatibleprocesses, thus can achieve the scale of mass production. Anotherbenefit is that the control circuit layout for controlling the DMFC andexternal circuit can be integrated on the substrate 210 or 510.

A method for fabricating integrated thin cathode electrode sheet 200 andintegrated thin anode electrode sheet 500 of the DMFC 20 is nowdescribed in detail with reference to FIG. 4 to FIG. 12. According tothis invention, the method for fabricating integrated thin cathodeelectrode sheet 200 and integrated thin anode electrode sheet 500 of theDMFC 20 is compatible with standard PCB processes.

First, as shown in FIG. 4, a CCL (Copper Clad Laminate) substrate 30 isprovided. The CCL substrate 30 is commercially available and has athickness of few millimeters. The CCL substrate 30 comprises a baselayer 32, a copper layer 34 laminated on an upper surface of the baselayer 32, and a copper layer 36 laminated on a lower surface of the baselayer 32.

As shown in FIG. 5, a conventional drilling process is carried out todrill a plurality of through holes 42 in the CCL substrate 30 withinpre-selected electrode areas (not explicitly shown). In accordance withthe preferred embodiment, the surface area of the through holes 42within a pre-selected electrode area is preferably more than 50% of thesurface area of the pre-selected electrode area.

Subsequently, as shown in FIG. 6, a thin copper layer 46 is chemicallydeposited on the CCL substrate 30 and on the exposed interior sidewallsof the through holes 42. It is noted that the copper layer 46 isdeposited in a non-selective manner.

As shown in FIG. 7, a patterned resist (dry film) 48 is formed on theCCL substrate 30 to define the electrode area 49. Taking the integratedcathode electrode sheet 200 of FIG. 3 as an example, the electrode area49 defined by the patterned resist 48 is one of the cathode electrodeareas 201˜205. Not shown in FIG. 7, the patterned resist 48 also definesthe conductive wires 250˜254 and the positive electrode node 261. It isnoted that the conductive via through holes 211˜215 of the integratedcathode electrode sheet 200 are formed simultaneously with the throughholes 42 in the same drilling process. Taking the integrated anodeelectrode sheet 500 of FIG. 3 as an example, the electrode area 49defined by the patterned resist 48 is one of the anode electrode areas501˜505, and the patterned resist 48 also defines the conductive pads511˜515 (not shown in FIG. 7).

As shown in FIG. 8, using the patterned resist 48 as a plating mask, anelectroplating process is carried out to form a copper layer 62 on theCCL substrate 30 where is not covered by the patterned resist 48including the electrode area 49. A tin/lead (Sn/Pb) composite layer 64is then electroplated on the copper layer 62.

As shown in FIG. 9, the patterned resist 48 is stripped to expose therest of the copper layer 46.

As shown in FIG. 10, a copper etching process such as conventional wetetching is then carried out to etch away the copper layer 46 and thecopper layers 34 and 36 that are not covered by the Sn/Pb layer 64.After this, another etching process is carried out to etch away theSn/Pb layer 64, thereby exposing the remaining copper layer 62. At thisstage, the fabrication of the integrated anode electrode sheet 500 ofFIG. 3 is complete.

To complete the fabrication of the integrated cathode electrode sheet200 of FIG. 3, there are still few steps to go. As shown in FIG. 11, toprevent short-circuiting caused during the subsequent soldering processand potential damages to the substrate, a solder resist layer 72 iscoated. The solder resist layer 72 may be made of materials that arecommercially available and are commonly used in conventional PCBprocesses. Preferably, the solder resist layer 72 is made ofphotosensitive materials that can be patterned by using conventionallithographic process to define the protected area on the electrode sheet200.

As shown in FIG. 12, optionally, to further protect the integratedcathode electrode sheet 200 from oxidation due to long-term contact withair, a conductive protection layer 74 is coated on the electrode. Theconductive protection layer 74 may be made of nickel/gold (Ni/Au),tin/lead (Sn/Pb), or chemical silver.

Nevertheless, the assembly of the integrated thin cathode electrodesheet 200, the MEA unit 300, the intermediate bonding layer 400, and theintegrated thin anode electrode sheet 500 still has a significantdisadvantage. Please refer to FIG. 18 and FIG. 19. FIG. 18 is aperspective diagram showing a stage before the integrated thin cathodeelectrode sheet 200, the MEA unit 300, the intermediate bonding layer400, and the integrated thin anode electrode sheet 500 are laminatedwhereas FIG. 19 is a diagram showing a stage after the integrated thincathode electrode sheet 200, the MEA unit 300, the intermediate bondinglayer 400, and the integrated thin anode electrode sheet 500 arelaminated. As shown in FIG. 19, the excess resin 900 that is compressedduring the laminating process will overflow and plug the conductive viaholes 411 and eventually cause a circuit disconnection between the anodeand cathode.

Please refer to FIG. 13 and FIG. 14. FIG. 13 and FIG. 14 are side-viewdiagrams showing the means by which the integrated thin cathodeelectrode sheet 200, the MEA unit 300, the intermediate bonding layer400, and the integrated thin anode electrode sheet 500 are assembledaccording to another embodiment of the present invention. At first, theconductive pads 511-515 are fabricated into the conductive via throughholes 511′-515′. As shown in FIG. 13, a metal plug, such as a rivet 711,is then used for aligning and penetrating through the conductive viathrough hole 211 of the integrated thin cathode electrode sheet 200, theconductive via through hole 411 of the intermediate bonding layer 400,and the conductive via through hole 511′ of the integrated thin anodeelectrode sheet 500. Next, the integrated thin cathode electrode sheet200, the MEA unit 300, the intermediate bonding layer 400, and theintegrated thin anode electrode sheet 500 are laminated together forforming a bipolar/MEA assembly 750, which can further be fabricated intoa fuel cell with a fuel base (not shown). According to the presentinvention, the rivet 711 used for conducting the integrated cathodeelectrode sheet 200 can be comprised of conductive materials such asaluminum, tin, or copper-zinc alloy.

Please refer to FIG. 15 to FIG. 17. FIG. 15 to FIG. 17 are side-viewdiagrams showing the means by which the integrated thin cathodeelectrode sheet 200, the MEA unit 300, the intermediate bonding layer400, and the integrated thin anode electrode sheet 500 are assembledaccording to another embodiment of the present invention. At first, theconductive pads 511-515 are fabricated into the conductive via throughholes 511′-515′. As shown in FIG. 15, the integrated thin cathodeelectrode sheet 200, the MEA unit 300, the intermediate bonding layer400, and the integrated thin anode electrode sheet 500 are aligned andlaminated together for forming a bipolar/MEA assembly 850, as shown inFIG. 16. Since the resin utilized during the lamination process caneasily plug the conductive via through holes, a screw 811 a and a screwnut 811 b are used as metal plugs for penetrating the plugged conductivevia through holes and facilitating the conductivity of the bipolar/MEAassembly 860.

To sum up, the present invention flat panel type DMFC encompasses atleast the following advantages.

(1) The cost per cell is reduced since the starting material, CCLsubstrate, is cheaper. Besides, the process of fabricating the germaneparts, the integrated thin cathode electrode sheet 200 and integratedthin anode electrode sheet 500 of the DMFC 20, is compatible with maturePCB processes.

(2) The process of fabricating the germane parts, the integrated thincathode electrode sheet 200 and integrated thin anode electrode sheet500 of the DMFC 20, is compatible with mature PCB process. Theproduction cost is therefore reduced.

(3) No bended bipolar wire lath is needed. The manufacture of theintegrated thin cathode electrode sheet 200 and integrated thin anodeelectrode sheet 500 can therefore achieve the scale of mass production.Direct stack assembly is more precise.

(4) The control circuit layout for controlling the lithium battery ofportable apparatus, the DMFC and the external circuit can besimultaneously fabricated on the laminate substrate, thus reducing thesize of the DMFC and increasing the integrity of the DMFC.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A method for assembling a flat panel direct methanol fuel cell, themethod comprising: providing an integrated cathode electrode sheetcomprising a first substrate, a plurality of cathode electrode areas,and a first conductive via through hole, wherein the cathode electrodeareas are electroplated on both the front and the backside of the firstsubstrate and have a plurality of apertures therein, wherein the firstconductive via through hole is disposed outside the cathode electrodeareas and is electronically connected to the respective cathodeelectrode areas with a conductive wire; providing a plurality of protonexchange membranes corresponding to the plurality of cathode electrodeareas; providing an intermediate bonding layer comprising at least onebonding sheet, wherein the intermediate bonding layer comprises aplurality of openings for respectively accommodating the plurality ofproton exchange membranes, and a second conductive via through hole thatis aligned with the first conductive via through hole; providing anintegrated anode electrode sheet comprising a second substrate, aplurality of anode electrode areas corresponding to the plurality ofcathode electrode areas, and a third conductive via through holecorresponding to the first conductive via through hole; stacking theintegrated cathode electrode sheet, the plurality of proton exchangemembranes, the intermediate bonding layer, and the integrate anodeelectrode sheet in order; aligning and penetrating the first conductivevia through hole, the second conductive via through hole, and the thirdconductive via through hole by using a metal plug; utilizing the metalplug to conduct and to fix the first conductive via through hole, thesecond conductive via through hole, and the third conductive via throughhole in place for forming a bipolar/MEA assembly; and combining thebipolar/MEA assembly with a fuel container.
 2. The method of claim 1,wherein the cathode electrode area comprises a copper clad base layer, achemically deposited copper layer on the copper clad base layer, anelectroplated copper layer formed on the chemically deposited copperlayer, and a conductive protection layer on the electroplated copperlayer.
 3. The method of claim 2, wherein the conductive protection layercomprises Ni/Au.
 4. The method of claim 1, wherein the proton exchangemembrane is a solid-state proton exchange membrane.
 5. The method ofclaim 1, wherein bonding sheet is comprised of “Prepreg” B-stage resin.6. The method of claim 1, wherein the first substrate is comprised ofglass fiber reinforced polymeric materials.
 7. The method of claim 6,wherein the glass fiber reinforced polymeric materials compriseANSI-grade FR-1, FR-2, FR-3, FR-4, FR-5, CEM-1, or CEM-3.
 8. The methodof claim 1, wherein the metal plug is a rivet.
 9. The method of claim 1,wherein the metal plug is a screw.
 10. A flat panel direct methanol fuelcell (DMFC) comprising: an integrated cathode electrode sheet comprisinga first substrate, a plurality of cathode electrode areas, a firstconductive via through hole, wherein the cathode electrode areas areelectroplated on both the front and the backside of the first substrateand have a plurality of apertures therein, wherein the first conductivevia through hole is disposed outside the cathode electrode areas and iselectronically connected to the respective cathode electrode areas witha conductive wire; a plurality of proton exchange membranescorresponding to the plurality of cathode electrode areas; anintermediate bonding layer comprising at least one bonding sheet,wherein the intermediate bonding layer comprises a plurality of openingsfor respectively accommodating the plurality of proton exchangemembranes, and a second conductive via through hole that is aligned withthe first conductive via through hole; an integrated anode electrodesheet comprising a second substrate, a plurality of anode electrodeareas disposed corresponding to the plurality of cathode electrodeareas, and a third conductive via through hole corresponding to thefirst conductive via through hole, wherein the integrated cathodeelectrode sheet, the plurality of proton exchange membranes, theintermediate bonding layer, and the integrate anode electrode sheet arestacked in order; a metal plug aligning and conducting the firstconductive via through hole, the second conductive via through hole, andthe third conductive via through hole; and a fuel container.
 11. Theflat panel direct methanol fuel cell of claim 10, wherein the cathodeelectrode area comprises a copper clad base layer, a chemicallydeposited copper layer on the copper clad base layer, an electroplatedcopper layer formed on the chemically deposited copper layer, and aconductive protection layer on the electroplated copper layer.
 12. Theflat panel direct methanol fuel cell of claim 11, wherein the conductiveprotection layer comprises Ni/Au.
 13. The flat panel direct methanolfuel cell of claim 10, wherein the proton exchange membrane is asolid-state proton exchange membrane.
 14. The flat panel direct methanolfuel cell of claim 10, wherein bonding sheet is comprised of PrepregB-stage resin.
 15. The flat panel direct methanol fuel cell of claim 10,wherein the metal plug is a rivet.
 16. The flat panel direct methanolfuel cell of claim 10, wherein the metal plug is a screw.